1) Field of the Invention
This invention relates to novel bifunctional chelating agents derived from 4,8-dihydroxyquinoline-2-carboxylic acid, useful in radioisotopic labeling of organic substrates. In one aspect this invention relates to chelating agents which have the ability to react with compounds of biological or clinical interest to form derivatives which will chelate suitable radionuclides, resulting in radioisotopic labeling of the compounds. The bis-quinolinol chelates of the invention are particularly useful as imaging agents for investigating organ functions in warm blooded animals, and for localizing radioactivity for diagnostic or therapeutic purpose.
2) Description of the Related Art
It is known that chelating agents such as ethylenediaminetetraacetic acid dianhydride (EDTA-dianhydride) or diethylenetriaminepentaacetic acid dianhydride (DTPA dianhydride) can be directly coupled to biological substrates to form conjugates which can be labeled with radionuclides used in in vivo imaging applications. However, EDTA and DTPA conjugates have shown limitations as to the variety of radionuclides that can be chelated, and as to their in vivo stabilities.
Accordingly, one or more of the following objects will be achieved by the practice of the present invention. It is an object of this invention to provide bis-quinolinols which are capable of forming chelates with a variety of radionuclides. Another object of this invention is to provide bifunctional bis-quinolinols which can be readily coupled to biological substrates, and the conjugates so formed can then be labeled with radionuclides which are suitable for diagnosis and therapy. It is a further object of the invention to provide radioisotope labeled compounds possessing superior in vivo stabilities. These and other objects will readily become apparent to those skilled in the art in the light of the teachings herein set forth.